EP2C20F256C8N Datasheet, PDF (365/470 Pages) Altera Corporation – Cyclone II Device Handbook, Volume 1

Altera Corporation
February 2007
Configuring Cyclone II Devices
Cyclone II devices offer an optional INIT_DONE pin which signals the
end of initialization and the start of user mode with a low-to-high
transition. The Enable INIT_DONE output option is available in the
Quartus II software from the General tab of the Device & Pin Options
window. If you use the INIT_DONE pin, an external 10-kΩ pull-up
resistor is required to pull the signal high when nCONFIG is low and
during the beginning of configuration. Once the optional bit to enable
INIT_DONE is programmed into the device (during the first frame of
configuration data), the INIT_DONE pin goes low. When initialization is
complete, the INIT_DONE pin is released and pulled high. This
low-to-high transition signals that the FPGA has entered user mode. If
you do not use the INIT_DONE pin, the initialization period is complete
after CONF_DONE goes high and 299 clock cycles are sent to the CLKUSR
pin or after the time t_CF2UM (see Table 13–8) if the Cyclone II device uses
the internal oscillator.
User Mode
When initialization is complete, the FPGA enters user mode. In user
mode, the user I/O pins no longer have weak pull-up resistors and
function as assigned in your design.
When the Cyclone II device is in user mode, you can initiate
reconfiguration by pulling the nCONFIG signal low. The nCONFIG signal
should be low for at least 2 µs. When nCONFIG is pulled low, the
Cyclone II device is reset and enters the reset stage. The Cyclone II device
also pulls nSTATUS and CONF_DONE low and all I/O pins are tri-stated.
Once nCONFIG returns to a logic high level and nSTATUS is released by
the Cyclone II device, reconfiguration begins.
Error During Configuration
If an error occurs during configuration, the Cyclone II device drives the
nSTATUS signal low to indicate a data frame error, and the CONF_DONE
signal stays low. If you enable the Auto-restart configuration after error
option in the Quartus II software from the General tab of the Device &
Pin Options dialog box, the Cyclone II device resets the serial
configuration device by pulsing nCSO, releases nSTATUS after a reset
time-out period (about 40 µs), and retries configuration. If the
Auto-restart configuration after error option is turned off, the external
system must monitor nSTATUS for errors and then pull nCONFIG low for
at least 2 µs to restart configuration.
1
If you use the optional CLKUSR pin and the nCONFIG pin is
pulled low to restart configuration during device initialization,
ensure CLKUSR continues to toggle during the time nSTATUS is
low (a maximum of 40 μs).
13–11
Cyclone II Device Handbook, Volume 1